It's about making sure you're talking with the 'right' people. Goodness knows, I'd not want to find myself getting all chummy with a bunch of Lancastrians!

It's along the same lines as "I've heard them talk." As in "Don't let the children play with them, Charles! I've heard them talk, they're from the North."

The flip side being what another colleague told me. His surname was Khan, and he was at a conference in London where a distinctly upper-class chap asked his name. On being told "Kahn", the posh guy, without batting an eyelid, asked "Is that the Wiltshire Khans or the Sussex Khans?"